Methods of manufacturing a semiconductor device by forming a separation trench

ABSTRACT

A method of manufacturing a semiconductor device includes forming a separation trench into a first main surface of a semiconductor substrate and removing substrate material from a second main surface of the semiconductor substrate, so as to thin the substrate to a thickness of less than 100 μm, the second main surface being opposite to the first main surface, so as to uncover a bottom side of the trench. Additional methods of manufacturing semiconductor devices are provided.

TECHNICAL FIELD

The present disclosure relates to a method of manufacturing asemiconductor device and to a semiconductor workpiece.

BACKGROUND

Power devices, for example, MOS power transistors attempt to achieve asmall on-resistance which is defined by R_(on)·area, while at the sametime achieving a high breakdown voltage Vds when being in an off state.Approaches have been made to manufacture these power transistors on thinto ultra-thin substrates having a thickness of less than 100 μm, forexample 70 μm or less and having even a thickness of 10 to 20 μm,depending on the voltage class in which the device is being employed.

According to generally employed semiconductor manufacturing processes,components of semiconductor devices are processed by processingsemiconductor wafers. After manufacturing the single devices, the waferis isolated into single chips. When semiconductor devices aremanufactured on thin substrates, problems may arise when isolating thesingle chips by conventional isolation or dicing processes.

SUMMARY

According to an embodiment, a method of manufacturing a semiconductordevice comprises forming a separation trench into a first main surfaceof a semiconductor substrate, forming at least one sacrificial materialin the separation trench. The method further includes removing substratematerial from a second main surface of the semiconductor substrate, thesecond main surface being opposite to the first main surface, so as touncover a bottom side of the trench. The method further includesremoving the at least one sacrificial material from the bottom side ofthe trench, after the substrate material has been removed from thesecond main surface.

According to an embodiment, a semiconductor workpiece comprises asemiconductor substrate, at least two chip areas, components ofsemiconductor devices being formed in the semiconductor substrate in thechip areas, and a separation trench being disposed between adjacent chipareas. The separation trench is formed in a first main surface of thesemiconductor substrate and extends from the first main surface to asecond main surface of the semiconductor substrate, the second mainsurface being disposed opposite to the first main surface. Theseparation trench is filled with at least one sacrificial material.

According to an embodiment, a method of manufacturing a semiconductordevice in a semiconductor substrate comprising a first main surface, thesemiconductor substrate including chip areas, includes formingcomponents of the semiconductor device in the first main surface in thechip areas, removing substrate material from a second main surface ofthe semiconductor substrate, the second main surface being opposite tothe first main surface, forming a separation trench into a first mainsurface of a semiconductor substrate, the separation trench beingdisposed between adjacent chip areas, forming at least one sacrificialmaterial in the separation trench, and removing the at least onesacrificial material from the trench.

According to an embodiment, a method of manufacturing a semiconductordevice comprises: forming a separation trench into a first main surfaceof a semiconductor substrate; and removing substrate material from asecond main surface of the semiconductor substrate, so as to thin thesubstrate to a thickness of less than 100 μm, the second main surfacebeing opposite to the first main surface, so as to uncover a bottom sideof the trench.

According to an embodiment, a method of manufacturing a semiconductordevice comprises: forming a separation trench into a first main surfaceof a semiconductor substrate; forming at least one sacrificial materialin the separation trench; removing substrate material from a second mainsurface of the semiconductor substrate, the second main surface beingopposite to the first main surface, so as to uncover a bottom side ofthe trench; forming and patterning a further insulating layer on thesecond main surface after removing the substrate material from thesecond main surface of the semiconductor substrate; removing the atleast one sacrificial material from the bottom side of the trench, afterthe substrate material has been removed from the second main surface;and forming a conductive material on the second main surface afterremoving the at least one sacrificial material from the trench.

According to an embodiment, a method of manufacturing a semiconductordevice comprises: forming a separation trench into a first main surfaceof a semiconductor substrate; forming at least one sacrificial materialin the separation trench, the sacrificial material comprising a firstsacrificial layer adjacent to a sidewall of the separation trench, and asecond sacrificial layer, being different from the first sacrificiallayer, the first sacrificial layer being made of an insulating material;and removing substrate material from a second main surface of thesemiconductor substrate, the second main surface being opposite to thefirst main surface, so as to uncover a bottom side of the trench.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description and onviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification. The drawings illustrate the embodiments ofthe present invention and together with the description serve to explainprinciples of the invention. Other embodiments of the invention andintended advantages will be readily appreciated as they become betterunderstood by reference to the following detailed description.

FIGS. 1A to 1J illustrate a method of manufacturing a semiconductordevice according to an embodiment;

FIGS. 2A to 2H illustrate a method of manufacturing a semiconductordevice according to a further embodiment;

FIGS. 3A to 3E illustrate a method of manufacturing a semiconductordevice according to an embodiment;

FIGS. 4A to 4F illustrate a method of manufacturing a semiconductordevice according to a further embodiment;

FIG. 5 schematically illustrates a method of manufacturing asemiconductor device according to an embodiment; and

FIGS. 6A and 6B schematically illustrate a method of manufacturing asemiconductor device according to further embodiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which are shownby way of illustrations specific embodiments in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present invention. For example, featuresillustrated or described for one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present invention includes such modifications andvariations. The examples are described using specific language whichshould not be construed as limiting the scope of the appending claims.The drawings are not scaled and are for illustrative purposes only. Forclarity, the same elements have been designated by correspondingreferences in the different drawings if not stated otherwise.

The terms “having”, “containing”, “including”, “comprising” and the likeare open and the terms indicate the presence of stated structures,elements or features but not preclude additional elements or features.The articles “a”, “an” and “the” are intended to include the plural aswell as the singular, unless the context clearly indicates otherwise.

The term “electrically connected” describes a permanent low-ohmicconnection between electrically connected elements, for example a directcontact between the concerned elements or a low-ohmic connection via ametal and/or highly doped semiconductor.

The terms “wafer”, “substrate” or “semiconductor substrate” used in thefollowing description may include any semiconductor-based structure thathas a semiconductor surface. Wafer and structure are to be understood toinclude silicon, silicon-on-insulator (SOI), silicon-on sapphire (SOS),doped and undoped semiconductors, epitaxial layers of silicon supportedby a base semiconductor foundation, and other semiconductor structures.The semiconductor need not be silicon-based. The semiconductor could aswell be silicon-germanium, germanium, or gallium arsenide. According toembodiments of the present application, generally, silicon carbide (SiC)or gallium nitride (GaN) is a further example of the semiconductorsubstrate material.

The term “vertical” as used in this specification intends to describe anorientation which is arranged perpendicular to the first surface of thesemiconductor substrate or semiconductor body.

The terms “lateral” and “horizontal” as used in this specificationintends to describe an orientation parallel to a first surface of asemiconductor substrate or semiconductor body. This can be for instancethe surface of a wafer or a die.

Generally, for patterning material layers, a photolithographic methodmay be used in which a suitable photoresist material is provided. Thephotoresist material is photolithographically patterned using a suitablephotomask. The patterned photoresist layer can be used as a mask duringsubsequent processing steps. For example, as is common, a hardmask layeror a layer made of a suitable material such as silicon nitride,polysilicon or carbon may be provided over the material layer to bepatterned. The hardmask layer is photolithographically patterned usingan etching process, for example. Taking the patterned hardmask layer asan etching mask, the material layer is patterned.

FIG. 1A shows a cross-sectional view of a semiconductor workpieceaccording to an embodiment, which may form a starting point forimplementing a method according to an embodiment. Alternatively, theworkpiece may be obtained when performing the method according to anembodiment.

The workpiece may comprise a semiconductor substrate 100 having a firstmain surface 110 and a second main surface 120. The workpiece comprisesa chip area 150 and a kerf area 155. Generally, in a semiconductorsubstrate such as a semiconductor wafer, a plurality of chip areas 150are defined, adjacent chip areas 150 being separated from each other bya kerf area 155. Components of semiconductor devices are formed in eachof the chip areas 150. For example, transistors 160 and othersemiconductor devices may be formed in each of the chip areas 150. Thesemiconductor devices may comprise doped regions 161, conductive lines221 or pads, and insulating material. For example, components of thesemiconductor devices may be formed in the semiconductor substrate 100or in a region adjacent to a first main surface 110 of the semiconductorsubstrate 100. Further components of the semiconductor devices may bedisposed outside the semiconductor substrate 100. For example,conductive lines 221, contact pads and other components may be formedover the semiconductor substrate 100 and may, for example, be disposedwithin an insulating layer 225. The chip area 150 may further compriseisolation trenches 130 being filled with at least one insulatingmaterial 131 such as silicon oxide. A further insulating or conductivematerial 132 may be disposed in the isolation trenches 130, the furtherinsulating or conductive material 132 being insulated from the substratematerial 100 by the insulating layer 131. For example, these isolationtrenches 130 may insulate adjacent portions of the chip area 150.

According to further embodiments, contact trenches having a similarconstruction as the isolation trenches 130 may be disposed within thesemiconductor substrate 100. For example, the further insulating orconductive material 132 may be conductive, so that an electrical contactfrom the first main surface 110 to the second main surface 120 may beaccomplished by the further insulating or conductive material 132. Forexample, a distance between the first main surface 110 and the secondmain surface 120 may be less than 100 μm, for example, less than 60 μm,for example 40 μm.

In the embodiment shown in FIG. 1A, an insulating layer 225 is disposedover the first main surface 110 of the semiconductor substrate 100. Asurface of the insulating layer 225 defines a surface 210 of theworkpiece 200.

Further, on a back side of the semiconductor substrate 100, a furtherinsulating layer 235 may be disposed so as to define a workpiece backside 220. Within the kerf area 155, for example, test structures, pads,contact pads 230 may be disposed so as to fulfil several functionsaccording to specific needs. For example, test structures or patternsfor monitoring a wafer processing method may be arranged in the kerfarea 155.

In the embodiment illustrated in FIG. 1A, a separation trench 140 isdisposed between the kerf area 155 and an adjacent chip area 150. Theseparation trench 140 is formed in the first main surface 110 of thesemiconductor substrate 100. The separation trench 140 extends in adirection intersecting the illustrated plane of the drawing. Forexample, the separation trench 140 may extend perpendicularly withrespect to the plane of the drawing. According to a further embodiment,depending on the desired shape of the resulting chips, the separationtrench 140 may extend in an arbitrary direction intersecting the planeof the drawing. The separation trench 140 is filled with at least onesacrificial material. For example, the sacrificial material may comprisea first sacrificial layer 141 which may be insulating. The firstsacrificial layer 141 is disposed adjacent to a sidewall of theseparation trench 140. The first sacrificial layer 141 extends along thesidewall of the separation trench 140 to a bottom side 144 thereof.Moreover, the interior of the separation trench 140 may be filled with asecond sacrificial layer 142 which is different from the first material.For example, the first layer 141 may be insulating and the secondsacrificial layer 142 may be conductive. In the embodiment illustratedin FIG. 1A, the separation trench 140 extends from the first mainsurface 110 of the semiconductor substrate 100 to the second mainsurface 120 of the semiconductor substrate 100. The separation trench140 may be completely filled with the sacrificial material so that thesacrificial filling is flush with the first main surface 110. Thesacrificial material may comprise silicon oxide, for example, thermallygrown silicon oxide, silicon nitride or polysilicon and any combinationof these materials. According to the embodiment illustrated in FIG. 1A,the workpiece surface 210 may be a planar surface. Further, thesemiconductor substrate 100 may be attached to a front side carrier 300such as a glass carrier so that the first workpiece surface 210 isadjacent to the front side carrier 300. Although FIG. 1A explicitlyshows a kerf area, it will be readily appreciated that according to afurther embodiment the kerf area 155 may be omitted and separation ofthe single chips may be accomplished using the separation trenches 140.

According to an embodiment, the separation trench 140 may be formed bydry etching, for example plasma etching. According to an embodiment, theseparation trench 140 may be formed before forming components of thesemiconductor devices. Optionally, the separation trench 140 may beformed by a high temperature process before forming those components ofthe semiconductor device which are sensitive to high temperature. Forexample, the separation trench 140 and the isolation trench 130 may beformed by a joint etching step. According to a further embodiment, theseparation trench 140 may be formed after thinning the semiconductorsubstrate 100.

Starting from the pre-processed workpiece shown in FIG. 1A, the backside 220 of the workpiece may be processed, by, optionally, forming ahard mask layer (stack) on the workpiece back side 220, followed by aphotoresist layer 240. Thereafter, openings 241 may be defined in thephotoresist layer 240. For example, the openings 241 may be defined soas to be aligned with the position of the filling made of the secondsacrificial layer 142 inside the separation trenches 140. Whenphotolithographically defining the openings 241, the isolation trenches130 may be used as a positioning mark. Thereafter, a further etchingstep may be performed so as to remove the first sacrificial layer 141.In the embodiment shown in FIG. 1B, since the isolation trench 130 has afunction different from that of the separation trench 140, no opening isformed so as to be aligned with the position of the second layer 132inside the isolation trench 130.

Thereafter, an etching step may be performed so as to define openings231 in the insulating layer 235. For example, wet etching withhydrofluoric acid (HF) may be performed so as to form the openings. FIG.1C shows an example of a resulting structure. The openings 231 mayapproximately have a width corresponding to a width of the separationtrenches 140. Nevertheless, the width of the openings 231 should belarge enough so that the whole cross-section of the second sacrificiallayer 142 is uncovered. Thereafter, the second sacrificial layer 142 isremoved from the separation trenches 140. For example, if polysilicon isused as the second sacrificial material, etching with KOH may beemployed. According to an embodiment, etching is performed from the backside 220 of the substrate. Hence, removing the at least one sacrificialmaterial from the trench comprises removing the at least one sacrificialmaterial from the bottom side 144 of the trench or from the back side220 of the substrate. Differently stated, removing the at least onesacrificial material may comprise etching the second sacrificial layer142 adjacent to the second main surface 120 of the substrate.

FIG. 1D shows an example of a resulting structure. As is shown, now agap 143 is formed between the sidewalls of the separation trench 140.The gap 143 extends from the second main surface 120 of thesemiconductor substrate 100 to approximately the first main surface 110of the semiconductor substrate 100. In the context of the presentapplication, the term “extends to approximately the first main surfaceof the semiconductor substrate” means that a small amount of materialmay remain within the gap, as long as the small amount does not inhibitor prevent a separation process which will be explained in thefollowing. For example, a remaining amount of material may have athickness (dimension in the vertical direction) of 0 to 500 nm.

Then, a further etching step, for example, an isotropic wet etching stepusing, for example, HF, may be performed so as to form openings 226 inthe insulating layer 225. FIG. 1E shows an example of a resultingstructure. The gap 143 now extends to the workpiece surface 210.

FIG. 1F shows an example of a resulting structure after removing theresidues of the photoresist layer 240. Then, the structure istransferred to a foil 400, which may be a foil suitable for separatingthe wafer into single chips. For example, the foil 400 may be made of asuitable plastic or polymer, as it is conventional.

FIG. 1G shows an example of a resulting structure. In the next step, thewafer may be separated into single chips by removing the foil 400according to generally known methods. By way of example, the foil 400may be stretched, and UV light may be irradiated from the back side 220to separate the single chips from the foil 400. Since the separation orisolation of the wafer into chips has been accomplished by the severaletching steps, it is not necessary to separate the single chips bydicing or sawing the substrate material 100 as well as the layers formedon the semiconductor substrate 100. As a consequence, the semiconductormaterial is less likely to be damaged due to the mechanical dicingprocess. Further, the width of the kerf area 155 may be reduced sincethere is less material necessary in order to perform the separationprocess. For example, the width of the kerf area 155 may beapproximately 30 to 40 μm.

According to a further embodiment, separation of the single chips may beaccomplished by removing the foil 400 according to known processes.

As has been explained above, according to an embodiment, the separationtrenches 140 may be defined at a very early processing stage of thesemiconductor device, before defining temperature sensitive components.As a result, the separation trenches can be etched using a hightemperature etching method. Further, the separation trenches 140 may bedefined photolithographically and may be etched by plasma etching, sothat, for example, crystal orientations do not need to be taken intoaccount during etching. As a result, it is possible to define thegeometry of the single chips photolithographically. Hence, any suitableshape of the single chips may be selected.

FIG. 1H shows an example of examples of shapes of the single chips. Forexample, as is shown in the left-hand part of FIG. 1h , the chip area150 may be approximately rectangular, with rounded corners. Separationtrenches 140 are disposed between the chip area 150 and the kerf area155. The kerf area 155 is disposed between adjacent chip areas 150. Asshown in the right-hand portion of FIG. 1H, the chip area 150 may alsohave the shape of hexagon.

FIG. 1I illustrates a portion of a chip area 150 and a kerf area 155according to an embodiment. As is shown, the kerf area 155 may befurther patterned in a direction parallel to the plane of thecross-section illustrated in FIGS. 1A to 1H by forming additionalseparation grooves 156 extending in a direction perpendicularly withrespect to the separation trenches 140. For example, the separationgrooves 156 may be formed by etching the material in the kerf using anappropriate photoresist mask. According to an embodiment, the separationgrooves 156 may have a similar structure as the separation trenches 140that have been described hereinbefore. Due to the presence of theadditional separation grooves 156, the kerf area 155 may be patternedand isolated into small pieces so that during the next processing steps,large kerf areas are prevented from being separated from the wafer.

FIG. 1J shows a further embodiment, according to which, starting fromthe structure shown in FIG. 1G, a further etching step using, forexample, KOH is performed no as to define tapered openings 232. Due tothe etching with KOH, the tapered openings 232 are etched isotropically.

FIG. 2 illustrates a method according to a further embodiment. Astarting point for the further embodiment is a semiconductor substrate100 comprising a chip area 150 and a kerf area 155 as has been explainedabove with reference to FIG. 1A.

According to the embodiment shown in FIG. 2A, separation trenches 140are etched in the first main surface 110 of the semiconductor substrate100. Further, isolation trenches 130 may be defined in the first mainsurface 110 of the semiconductor substrate 100. An insulating material131, 141 may be disposed adjacent to the sidewalls of the isolationtrench 130 and the separation trench 140. Further, a second sacrificiallayer 142 such as polysilicon may be disposed in the interior of theseparation trenches 140. Differing from the embodiment shown in FIG. 1A,the semiconductor substrate 100 of FIG. 2A has not been thinned.Accordingly, the distance between the second main surface 120 and thefirst main surface 110 corresponds to the usual thickness of asemiconductor wafer. The isolation trenches 130 and the separationtrenches 140 do not extend to the second main surface 120. Theinsulating material 131, 141 is disposed in the isolation trench 130 andthe separation trench 140, respectively, to extend to a bottom side 144of these trenches. An insulating layer 225 is disposed over thesemiconductor device components disposed in the chip area 150. Theinsulating layer 225 may also be disposed over contacts and conductivelines 230, 221 disposed in the kerf area 155. According to theembodiment shown in FIG. 2A, no frontside carrier is attached to theworkpiece surface 210. Hence, test procedures and measurements may beperformed in the kerf area 155. The insulating layer 225 has a planarsurface. Thereafter, a photoresist layer 240 is formed over theinsulating layer 225 and is patterned to form an etching mask. Then, theoxide layer is etched to form openings 227.

FIG. 2B shows an example of a resulting structure. In a next step, aninsulating material such as a polyimide layer 228 is formed over theresulting structure after removing the residues of the photoresist layer240. Further, the polyimide layer 228 is photolithographicallypatterned. Due to the presence of the polyimide layer 228 which isdisposed over the patterned oxide layer, the wafer has increasedmechanical robustness.

FIG. 2C shows an example of a resulting structure. As is shown, in thechip area 150, the insulating layer 225 is covered by the polyimidelayer 228, whereas the insulating layer 225 disposed in the kerf area155 is uncovered. Further, at the position of the openings 227, thesemiconductor substrate material 100 and the separation trenches 140 areuncovered. A surface of the polyimide layer 228 forms a workpiecesurface 210. As is shown, the workpiece surface is not flat but has atopology. In the next step, a suitable carrier 300 such as a glasscarrier is attached to the main surface 210 of the workpiece 200.

Thereafter, the semiconductor substrate 100 is thinned from the secondmain surface 120. For example, the semiconductor substrate 100 may bethinned by mechanically grinding, followed by CMP so as to cure defectswhich may be caused due to the grinding. For example, about 750 μmthickness of the semiconductor wafer may be removed.

FIG. 2D shows an example of a resulting structure. The shownsemiconductor substrate 100 has a thickness of less than 100 μm. Forexample, the thickness may be about 10 to 100 μm. At a thickness largerthan 100 μm, it becomes difficult to define an isolation trench 130 andthe separation trench 140 having the desired geometry. Thereafter, aphotoresist layer 240 may be formed on the second surface 120 of thesemiconductor substrate 100 and may be patterned so as to form openings241.

FIG. 2E shows an example of a resulting structure. Then, optionally, anisotropic etching step, for example using KOH, may be performed so as toform openings 232 in the substrate material 100.

FIG. 2F shows an example of a resulting structure. Thereafter, anetching step is performed so as to remove the insulating layer (firstsacrificial layer) 141 from the separation trenches 140. According tothe embodiment of FIG. 2F, the first sacrificial layer 141 is removedfrom the bottom side 144 of the trench. Differently stated, etching isperformed from the back side 120 of the semiconductor substrate 100.Further, the residues of the photoresist layer 240 are removed.

FIG. 2G shows an example of a resulting structure. As is shown, a gap143 is formed between the sidewalls of the separation trench 140. Thegap 143 extends from the second main surface 120 to approximately thefirst main surface 110 of the semiconductor substrate 100. Residues ofthe sacrificial filling 142 are disposed within the gap 143. Thereafter,the semiconductor substrate 100 is transferred to a foil so that thesecond main surface 120 of the semiconductor substrate 100 is adjacentto the foil 400. The glass carrier 300 is removed from the surface ofthe workpiece 210 by conventional methods.

FIG. 2H shows an example of a resulting structure. Due to the transferprocess, the residues of the sacrificial material 142 may drop.Thereafter, the semiconductor substrate 100 may be separated into singlechips by removing the foil 400.

A starting point of a further embodiment is the structure illustrated inFIG. 3A which corresponds to the structure shown in FIG. 2D. Thecomponents shown in FIG. 3A correspond to those which have beenillustrated with reference to FIGS. 1 and 2. According to the embodimentillustrated in FIG. 3, the sidewall insulating material 141, which maybe for example, a silicon oxide layer, remains at the sidewalls of theseparation trenches 140 during the processing method so as establish asidewall oxide of the resulting chips. An insulating layer 235 such as asilicon oxide layer is formed on the second main surface 120 of thesemiconductor substrate 100. Optionally, metal pads may be formedadjacent to the second main surface 120 before forming the insulatinglayer 235 so as, for example, to be in contact with the conductivefilling 132 of the isolation trench 130. Thereafter, a photoresistmaterial 240 is formed over the insulating layer 235. Further, openings241 are defined in the photoresist material 240.

FIG. 3B shows an example of a resulting structure. Using the patternedphotoresist layer 240 as an etching mask, openings 231 are formed in theinsulating layer 235. The openings 241 in the photoresist layer 240 and,thus, the openings 231 in the insulating layer 235 are positions overthe sacrificial material 142 in the separation trenches 140.

FIG. 3C shows an example of a resulting structure. Thereafter, theresidues of the photoresist layer 240 are removed, followed by a wetetching step so as to remove the sacrificial material 142 from theseparation trenches 140. According to the embodiment of FIG. 3C, etchingis performed from the back side of the semiconductor substrate 100.

FIG. 3D shows an example of a resulting structure. As is shown, thesidewalls of the substrate material 100 and the second main surface 120are covered by the insulating layer 132 in the chip areas 150 and in thekerf area 155. Further, a gap 143 is disposed between the sidewalls ofthe separation trench 140. The gap 143 extends from the second mainsurface 120 to approximately the first main surface 110. Thereafter, theresulting structure is transferred to the foil 400. Further, the glasscarrier is removed from the surface 210 of the workpiece 200 accordingto a conventional method. According to embodiments, the kerf area 155may be patterned in more detail, e.g. in a plane disposed before orbehind the depicted plane of the drawing. According to this embodiment,it is possible that the patterned pieces of the kerf area 155 drops whenthe transfer to the foil 400 takes place.

Thereafter, the foil 400 may be removed an as to separate the processedsemiconductor substrate 100 into single chips.

Starting point for the embodiment which is illustrated in FIG. 4 is thestructure shown in FIG. 3A. According to this embodiment, an insulatinglayer disposed on the back side of the substrate is patterned. Afterremoving at least one sacrificial material from the trench, a conductivelayer is formed and patterned on the back side.

Starting from the structure shown in FIG. 3A, an insulating layer 235 isformed on the second main surface 120 of the semiconductor substrate100. Thereafter, a photoresist layer 240 is formed on the insulatinglayer 235 and patterned. FIG. 4A shows an example of a resultingstructure. Then, using the patterned photoresist layer 240 as an etchingmask, etching is performed so as to partially remove the insulatinglayer 235 and a further photoresist layer 245 is formed over theresulting surface. In a next step, openings 241 are defined in thephotoresist layer 240.

FIG. 4B shows an example of a resulting structure. As is shown, theinsulating layer 235 is formed over a portion of the second main surface120 of the semiconductor substrate 100. Thereafter, openings 231 areformed in the insulating layer 235, using the patterned photoresistlayer 240 as an etching mask.

FIG. 4C shows an example of a resulting structure. Then, the sacrificialmaterial 142 is removed from the separation trenches 140 by etching.According to the embodiment shown in FIG. 4C, etching is performed fromthe back side of the semiconductor substrate 100. FIG. 4D shows anexample of a resulting structure. As is shown, a gap 143 is disposedbetween the sidewalls of the separation trench 140. The gap 143 extendsfrom the second main surface 120 to approximately the first main surface110 of the semiconductor substrate 100. The residues of the photoresistmaterial 240, 245 are removed, and a metal layer 246 may be formedadjacent to the second main surface 120 of the semiconductor substrate100. It is to be noted that the shown transistor 160 may be connected tothe metal layer 246 by means of a connection which is disposed before orbehind the shown drawing plane. Thereafter, the semiconductor substrate100 is transferred to a foil 400 and the glass carrier 300 may beremoved. FIG. 4F shows an example of a resulting structure. Thereafter,the semiconductor wafer may be separated into single chips by removingthe foil 400.

FIG. 5 illustrates a method of manufacturing a semiconductor deviceaccording to an embodiment in a flowchart. As is shown, a method ofmanufacturing a semiconductor device comprises forming a separationtrench into a first main surface of a semiconductor substrate (S10),forming at least one sacrificial material in the separation trench(S20), removing substrate material from a second main surface of thesemiconductor substrate (S30), the second main surface being opposite tothe first main surface, so as to uncover a bottom side of the trench,and removing at least one sacrificial material from the trench (S40),comprising etching the at least one sacrificial material adjacent to thesecond main surface.

According to a different interpretation, a method of manufacturing asemiconductor device comprises forming a separation trench into a firstmain surface of a semiconductor substrate (S10), forming at least onesacrificial material in the separation trench (S20), removing substratematerial from a second main surface of the semiconductor substrate(S30), the second main surface being opposite to the first main surface,so as to uncover a bottom side of the trench, and removing at least onesacrificial material from the trench (S40) so as to form a gap betweensidewalls of the separation trench, the gap extending from the secondmain surface to approximately the first main surface.

FIGS. 6A and 6B illustrate a method of manufacturing a semiconductordevice according to a further embodiment. According to the embodiment,the semiconductor device is formed in a semiconductor substratecomprising a first main surface, and the semiconductor substrateincludes chip areas. As is shown in FIG. 6A, the method comprisesforming components of the semiconductor device in the first main surfacein the chip areas (S110), removing substrate material from a second mainsurface of the semiconductor substrate (S120), the second main surfacebeing opposite to the first main surface, forming a separation trenchinto a first main surface of a semiconductor substrate (S130) betweenadjacent chip areas, forming at least one sacrificial material in theseparation trench (S140), and, thereafter, removing at least onesacrificial material from the trench (S150). According to the embodimentshown in FIG. 6A, the substrate material is removed from the second mainsurface (S120) before forming the separation trench (S130), and theseparation trench is formed to extend to the second main surface.

According to the embodiment shown in FIG. 6B, the separation trench isformed (S130) and the at least one sacrificial material is formed (S140)before removing the substrate material (S120), and the substratematerial is removed so as to uncover a bottom side of the trench.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the method comprising: forming a separation trench into a first mainsurface of a semiconductor substrate; forming at least one sacrificialmaterial in the separation trench, the sacrificial material comprising afirst sacrificial layer adjacent to a sidewall of the separation trench,and a second sacrificial layer, being different from the firstsacrificial layer and thereafter, removing substrate material from asecond main surface of the semiconductor substrate, so as to thin thesubstrate to a thickness of less than 100 μm, the second main surfacebeing opposite to the first main surface, so as to uncover a bottom sideof the trench.
 2. The method of claim 1, wherein the first sacrificiallayer is made of an insulating material.
 3. The method of claim 1,further comprising removing at least one sacrificial material from theseparation trench.
 4. The method of claim 1, further comprising: formingat least one layer on the second main surface of the semiconductorsubstrate so as to define a workpiece back side; and attaching thesemiconductor substrate to a back side carrier, so that the workpieceback side is attached to the back side carrier, after removing the atleast one sacrificial material from the separation trench.
 5. The methodof claim 4, wherein the semiconductor substrate is attached to the backside carrier after removing the at least one sacrificial material fromthe separation trench.
 6. The method of claim 1, further comprising:forming and patterning a further insulating layer on the second mainsurface after removing the substrate material from the second mainsurface of the semiconductor substrate; and forming a conductivematerial on the second main surface after removing the at least onesacrificial material from the trench.
 7. A method of manufacturing asemiconductor device, comprising: forming a separation trench into afirst main surface of a semiconductor substrate; forming at least onesacrificial material in the separation trench; thereafter, removingsubstrate material from a second main surface of the semiconductorsubstrate, so as to thin the substrate to a thickness of less than 100μm, the second main surface being opposite to the first main surface, soas to uncover a bottom side of the trench, and removing at least onesacrificial material from the separation trench.
 8. The method accordingto claim 7, wherein the separation trench is completely filled with theat least one sacrificial material.
 9. The method according to claim 7,wherein the sacrificial material comprises a first sacrificial layeradjacent to a sidewall of the separation trench, and a secondsacrificial layer, being different from the first sacrificial layer, thefirst sacrificial layer being made of an insulating material.
 10. Themethod according to claim 7, further comprising: forming at least onelayer on the second main surface of the semiconductor substrate so as todefine a workpiece back side; and attaching the semiconductor substrateto a back side carrier, so that the workpiece back side is attached tothe back side carrier, after removing the at least one sacrificialmaterial from the separation trench.
 11. The method according to claim10, wherein attaching the semiconductor substrate to the back sidecarrier is accomplished after removing the at least one sacrificialmaterial from the separation trench.
 12. The method of claim 7, furthercomprising: forming and patterning a further insulating layer on thesecond main surface after removing the substrate material from thesecond main surface of the semiconductor substrate; and forming aconductive material on the second main surface after removing the atleast one sacrificial material from the trench.